1. Field of the Invention
The present invention relates to an object detection apparatus, and more particularly, an object detection apparatus using an infrared signal. This application for the object detection apparatus is based on Korean patent application No. 1999-9593, which is incorporated by reference herein for all purposes.
2. Description of the Related Art
An object detection apparatus for detecting persons in a room typically employs passive sensors. The passive sensors detect thermal radiation from a person located in a certain detection angle range. The sensitivity of such an detection apparatus may be varied by an adjustment of the detection angle range of each passive sensor, which usually is set to be wide enough. The passive sensor, however, may operate erroneously according to the change of the room temperature and be influenced by an external interference. Accordingly, the object detection apparatus employing passive sensors can be used only in a room, but not out of a building. Further, the passive sensor cannot detect an object when the object is distant from the sensor, and thus is inadequate in an application where a precise detection is required.
In order to overcome such drawbacks, another conventional object detection apparatus uses an infrared beam to detect the presence of an object. The object detection apparatus comprises an infrared emitter constantly emitting the infrared beam and an infrared sensor disposed to face the infrared emitter and receiving the infrared beam from the emitter. When an object crosses a beam path between the infrared emitter and the infrared sensor, a blank period is introduced in the beam received by the infrared sensor. The apparatus detects the presence of the object by determining such a blank period. The apparatus, however, cannot determine the direction of the object, that is, whether the object enters or exits the room, when the object is detected.
As an approach for detecting the presence as well as the direction of the object passing through a gate, it can be contemplated to dispose a pair of the detection apparatuses in parallel and combine the detection data from the apparatuses. It is difficult to carry out arranging two detection apparatuses at a gate, however, because construction work has to be performed for four positions near the gate in addition to installing a separate module for combining detection data from the apparatuses.
On the other hand, the object detection apparatus is installed for each gate. In this regard, there has not been proposed a low cost system having a console for aggregating data from a plurality of object detection apparatuses, displaying synthetically the data or ringing a chime upon receiving a detection signal from one of the gates, and managing the apparatuses. Security providing companies operate a system for displaying data from multiple object detection apparatuses in a single display panel. Since being relatively expensive, however, it is inappropriate to install such a system in a small building having plural gates or independently in a single floor of a building.